A specialized type of heater apparatus is conventionally used for heating natural gas pipelines. The requirement for such heaters arises as a result of the possibility for condensation of water and hydrocarbon vapors, entrained in the natural gas, which can produce hydrates and resulting problems therefrom. The problem is conventionally avoided by heating the pipeline gas through the use of the specialized pipeline heater.
The need for pipeline heaters typically arises in locations along the pipeline or at well sites that are remote and often without an electrical supply available to operate conventional heaters. Typical types of such heaters include direct or indirect fired heaters, most often for heating a heat-transferring substance such as glycol, by a gas burner. The gas burner is ignited by a pilot light, the pilot light being a smaller gas burning flame.
Conventional heaters in use today often comprise manually operated pilot flame ignition systems without safety features for providing reliable re-lighting of an extinguished pilot flame. The heaters also include thermally operated main burner shut-off features. Therefore, the burners presently used are not reliable for avoiding condensation in the pipeline, and do not have the much needed safety features for detecting and reacting to burner pilot flame failure. Further, the burners presently used have continual pilot flames, regardless of infrequent burner use, resulting in wasted fuel due to unnecessary pilot burn time.
Burner controls and spark igniter devices are known and available for heaters used in other industries where the availability of power is not an issue. However, in industries where power is not readily available, such as in the case of pipelines, control and ignition remains an issue.
In order for electrically ignited gas burners to operate as stand-alone units without the need for connection to line voltage, attempts have been made to use electrical storage batteries for use as the power supply to the ignition circuits. Examples of such systems are taught in U.S. Pat. Nos. 3,174,534 and 3,174,535 to Weber and in U.S. Pat. No. 4,131,413 to Ryno. The Weber patents teach applying the battery power through an oscillation circuit across a transformer which supplies power to a spark gap. The battery is recharged after ignition by a thermopile charger, which receives energy from the flame. The Ryno patent similarly uses a battery supply which is recharged by a thermopile. Another concept available in the industry is to use solar energy to recharge the batteries.
While the introduction of rechargeable batteries, recharged by thermopiles or solar, is significant because gas burners are relatively maintenance-free over a lifetime of 15 years or more, the recharging circuit and rechargeable battery greatly increases the cost and complexity of the system. In addition, rechargeable batteries have a life expectancy of only three to five years and typically have performance issues in cold temperature operation and storage.